Development in the solar cell industry is driven by global environmental concerns and rising raw material prices. Among the various solar cells developed, CIGS solar cell (Cu(In,Ga)Se2) is advantageous as it can be fabricated with relatively lower costs due to its simpler fabrication process and ability for large area fabrication.
The semiconductor material with chalcopyrite structure mainly consists of the Group IB-IIIA-VIA compound which is a direct bandgap semiconductor material. The electronic and optical properties of the Group IB-IIIA-VIA compound are tunable by adjusting the proportion of its composition so that it can be applied to solar cells.
In prior art, a buffer layer is formed on a light absorption layer. A heterogeneous interface between the buffer layer and the light absorption layer is formed to improve short wavelength light absorption efficiency. Additionally, a non-toxic buffer layer (such as ZnS) is used instead of a toxic CdS buffer layer.
Furthermore, in the conventional fabrication method for the CIGS solar cell, a solution coating method is accompanied with a selenization process. However, due to this, a structural delamination problem occurs. When the ZnS buffer layer is formed on the delaminated light absorption layer, a high fabrication temperature is performed or a post-sulfurization process to the light absorption layer is performed to solve the structural delamination problem. However, for the post-sulfurization process, substrate selectivity is reduced due to the high fabrication temperature and a toxic material H2S is needed.